Customarily, vents in concrete walls were framed in connection with concrete wall forms so that when the concrete is poured and the forms removed, a vent aperture remains in the concrete. Vent frames have been developed to provide for construction of the vent aperture. There are several advantages to using a vent frame. For example, some vent frames allow screens or doors to be attached; others have a flared shape to channel water to the outside of the vent. In most cases, the foundation vent opening is easier to form with a vent frame.
Despite the advantages of vent frames currently used, some problems persist. For example, foundations are generally constructed with either a six-inch or an eight-inch thickness. However, with the current foundation vent frames, a different frame size must be used to accommodate each foundation thickness. Problems also persist with attachment of the vent frame to the panels or boards used to form the concrete and subsequent removal of the panels or boards from the vent frame. A foundation vent frame must be positioned accurately and the forms must be removable from the frame after the cement has cured.
One example of a prior art foundation vent frame is disclosed in U.S. Pat. No. 4,026,082 (Crofoot). The patent describes two identical frame structures that can be connected in a back-to-back relationship to form a single vent with walls that flare out from a juncture between the two frames. A screen may also be attached in the juncture between the two frames. The vent, however, only accommodates foundations of a single thickness. Different size frames must be manufactured depending on the thickness of the foundation wall into which the frame is to be disposed. Also, the methods the patent discloses for attachment of the frame to the forms (i.e., nailing the flanges of the frame to the forms or "supporting the frame on form ties") may not be easily carried out (see col. 3, lines 1-3). The "hard, stiff, plastic material" of which the vent is made can break while having a nail driven through it (see Col. 2, lines 40-42). Also, removal of the forms can be difficult without breaking the vent if the vent was nailed into place. Alternatively, supporting the vent on form ties may make accurate positioning and tight securing of the vent difficult.
A foundation vent box is also disclosed in U.S. Pat. No. 3,220,079 (Aggson). Aggson utilizes a two-piece vent that runs through a foundation. However, only one section of the vent spans the thickness of the foundation, leaving the other piece to simply cap the outside end of the vent with a removable vent screen. Due to a flexible flange portion, the vent box accommodates slight variations in distance between form panels. However, the purpose of the flexible flange is only to provide a constant engagement with the panels so as to preclude any passage of concrete therethrough. The vent does not accommodate radical changes in foundation wall thickness (e.g., six inches vs. eight inches). As with the Crofoot vent, the fastening of this vent into place between the forms and the removal of the forms can be difficult. The heads of nails driven through the flange may be embedded in cured concrete, making it difficult to pull the nails in order to remove the form.
Ventilator frames, not for use in forming foundation vents, have been developed that allow for variations in the thickness of a wall, floor, or ceiling. For example, a "ventilator thimble" is disclosed in U.S. Pat. No. 1,764,343 (Petrelli). The ventilator thimble includes telescoping sleeve structure that is biased to a collapsed position. The sleeves that comprise the sleeve structure have lips to avoid complete separation, but they do not lock into place at discrete widths. In fact, the object of the invention is to provide a ventilator that self-adjusts to the width between the ceiling of one room and the floor of a room above, being designed to mount in the space between the ceiling and the floor.
In consideration of the limitations and disadvantages of the devices and methods currently in use, it should be apparent that an effective solution to the problem of forming a foundation vent with a vent frame that can be used with foundations of various thicknesses and can be easily separated from concrete forms is not provided in the known prior art. Accordingly, the present invention was developed, and it provides significant advantages over previous devices or methods used to form foundation vents.